A Desert Graveyard in 3D
In the arid badlands of Patagonia, the La Buitrera fossil area holds the remains of a unique desert ecosystem from 98 million years ago. The site is part of the Candeleros Formation, a sequence of reddish sandstones deposited during the Cenomanian age of the Late Cretaceous. This ancient environment, known as the "Kokorkom" desert, consisted of a massive field of sand dunes interspersed with rivers and lakes. La Buitrera is extraordinary is its mode of preservation. Unlike many fossil sites where skeletons are crushed flat, the fine-grained sandstone here preserved animals in three dimensions. This exceptional fidelity allows paleontologists to study the delicate, hollow bones of small vertebrates without the distortion common to other deposits.
The locality has yielded a diverse collection of creatures that showed life in this Cretaceous desert. The assemblage includes sphenodonts (lizard-like reptiles), terrestrial crocodyliforms like Araripesuchus, and some of the earliest mammals found in South America. One of the most significant finds is Najash rionegrina, a primitive snake with well-developed hindlimbs, which has shows how snakes evolved from their lizard ancestors.
The Bird-Brained Raptors
The most celebrated fossils from La Buitrera are its dromaeosaurids—small, feathered predators related to Velociraptor. The star is Buitreraptor gonzalezorum, a slender, 1.5-meter-long raptor discovered in 2004. Buitreraptor belongs to the Unenlagiinae, a distinct subfamily of dromaeosaurids that evolved in the Southern Hemisphere. These southern raptors had different features from their northern cousins, including very long, narrow snouts filled with many small, unserrated teeth.
The 3D preservation of Buitreraptor skulls was perfect for modern analysis. Using high-resolution CT scanning, scientists created digital reconstructions of the brain cavity, or endocast. These scans revealed a brain shape surprisingly similar to that of modern birds, with large olfactory bulbs suggesting a keen sense of smell. The anatomy of the inner ear indicates excellent balance and the ability to coordinate rapid head and eye movements, important for a fast-moving predator. Another dromaeosaurid, Alnashetri cerropoliciensis, and other bird-like alvarezsaurid dinosaurs have also been found here, showing the evolution of small theropods.